After calling the crowds a brood of vipers, possibly singling out the many Pharisees and Sadducees who were there (Matthew), John challenged them to show their repentance with actions:

Luke 3:8 Prove by the way you live that you have repented of your sins and turned to God. Don’t just say to each other, ‘We’re safe, for we are descendants of Abraham.’ That means nothing, for I tell you, God can create children of Abraham from these very stones.

When the crowd asked what they should do, the answer was:

The crowds: If you have two shirts, give one to the poor. If you have food, share it with those who are hungry. (Luke 3:11)

The corrupt tax collectors: Collect no more taxes than the government requires.(Luke 3:13)